100A-15 |
Essential nutrient limitation and low-temperature conditioning for enhancing production of Type I ice nucleators by Pantoea ananatis |
W. BOONSUPTHIP and T. C. Lee. Food Science and The Center for Advanced Food Technology, Rutgers University, 65 Dudley Rd. Food Science Bldg., New Brunswick, NJ 08901 Limited availability of type I ice nucleators (INs) has hampered studies and application of INs. Several studies involving production of INs by bacteria have applied ecological imitation of low temperature and nutrient need of the bacteria to trigger and enhance the production of INs. However, it has never been tried on Pantoea ananatis (ATCC# 11530), a bacterium which liberate INs from the cells. We attempt to find a proper combination of essential nutrient limitation and low-temperature conditioning to enhance the production of type I INs by this bacterium. Our objective was to determine a proper growth conditioning for enhancing production of type I INs by the bacterium. The change in the level of the liberated INs [so-called extracellular ice nucleators (ECINs)] was also investigated. Growth conditionings included combinations of different essential nutrients and low-temperature conditionings. INA (–5°C) and total protein concentration in cell-free broth were used to evaluate enhancing strength of growth conditionings on type I IN and ECIN production. The bacterium was most sensitive to phosphorus and a temperature shift. Grown in a non-phosphorus medium at 32°C to a late-log phase, and shifted to 10°C for 3.5 hr, it maximally produced 4.02 x 108 type I INs/ml×OD600, 4.36 x 106 type I ECINs/mg Protein, and 0.03 mg Protein/ml×OD600. On the other hand, the other growth conditionings possessed far less enhancing effect (102-106 type I INs/ml×OD600, 103-105 type I ECINs/mg Protein, and 0.01-0.03 mg Protein/ml×OD600). This work confirms the concept of IN production enhancement in Pantoea ananatis by imitating the natural ecological conditions. This increase of the availability of type I INs and ECINs will provide opportunities for their basic and application studies.
Session 100A, Food Microbiology: General II
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